Ruby on Rails 3 Tutorial: From Zero to Deploy

Michael Hartl gets you started with Ruby on Rails by installing all the necessary software and setting up your development environment He'll then show you how to create your first Rails application, called (appropriately enough) first_app.

This chapter is from the book

This chapter is from the book

Welcome to Ruby on Rails™ 3 Tutorial: Learn Rails by Example. The goal of this book is to be the best answer to the question, "If I want to learn web development with Ruby on Rails, where should I start?" By the time you finish Ruby on Rails Tutorial, you will have all the knowledge you need to develop and deploy your own custom web applications. You will also be ready to benefit from the many more advanced books, blogs, and screencasts that are part of the thriving Rails educational ecosystem. Finally, since Ruby on Rails Tutorial uses Rails 3.0, the knowledge you gain here will be fully up to date with the latest and greatest version of Rails.1

Ruby on Rails Tutorial follows essentially the same approach as my previous Rails book,2 teaching web development with Rails by building a substantial sample application from scratch. As Derek Sivers notes in the foreword, this book is structured as a linear narrative, designed to be read from start to finish. If you are used to skipping around in technical books, taking this linear approach might require some adjustment, but I suggest giving it a try. You can think of Ruby on Rails Tutorial as a video game where you are the main character, and where you level up as a Rails developer in each chapter. (The exercises are the minibosses.)

In this first chapter, we'll get started with Ruby on Rails by installing all the necessary software and setting up our development environment (Section 1.2). We'll then create our first Rails application, called (appropriately enough) first_app. Rails Tutorial emphasizes good software development practices, so immediately after creating our fresh new Rails project we'll put it under version control with Git (Section 1.3). And, believe it or not, in this chapter we'll even put our first app on the wider web by deploying it to production (Section 1.4).

In Chapter 2, we'll make a second project, whose purpose will be to demonstrate the basic workings of a Rails application. To get up and running quickly, we'll build this demo app (called demo_app) using scaffolding (Box 1.1) to generate code; since this code is both ugly and complex, Chapter 2 will focus on interacting with the demo app through its URLs3 using a web browser.

In Chapter 3, we'll create a sample application (called sample_app), this time writing all the code from scratch. We'll develop the sample app using test-driven development (TDD), getting started in Chapter 3 by creating static pages and then adding a little dynamic content. We'll take a quick detour in Chapter 4 to learn a little about the Ruby language underlying Rails. Then, in Chapter 5 through Chapter 10, we'll complete the foundation for the sample application by making a site layout, a user data model, and a full registration and authentication system. Finally, in Chapter 11 and Chapter 12 we'll add microblogging and social features to make a working example site.

The final sample application will bear more than a passing resemblance to a certain popular social microblogging site—a site which, coincidentally, is also written in Rails. Though of necessity our efforts will focus on this specific sample application, the emphasis throughout Rails Tutorial will be on general principles, so that you will have a solid foundation no matter what kinds of web applications you want to build.

Sidebar 1.1. Scaffolding: Quicker, easier, more seductive

From the beginning, Rails has benefited from a palpable sense of excitement, starting with the famous 15-minute weblog video by Rails creator David Heinemeier Hansson, now updated as the 15-minute weblog using Rails 2 by Ryan Bates. These videos are a great way to get a taste of Rails' power, and I recommend watching them. But be warned: they accomplish their amazing fifteen-minute feat using a feature called scaffolding, which relies heavily on generated code, magically created by the Rails generate command.

When writing a Ruby on Rails tutorial, it is tempting to rely on the scaffolding approach—it's quicker, easier, more seductive. But the complexity and sheer amount of code in the scaffolding can be utterly overwhelming to a beginning Rails developer; you may be able to use it, but you probably won't understand it. Following the scaffolding approach risks turning you into a virtuoso script generator with little (and brittle) actual knowledge of Rails.

In Ruby on Rails Tutorial, we'll take the (nearly) polar opposite approach: although Chapter 2 will develop a small demo app using scaffolding, the core of Rails Tutorial is the sample app, which we'll start writing in Chapter 3. At each stage of developing the sample application, we will generate small, bite-sized pieces of code—simple enough to understand, yet novel enough to be challenging. The cumulative effect will be a deeper, more flexible knowledge of Rails, giving you a good background for writing nearly any type of web application.

1.1 Introduction

Since its debut in 2004, Ruby on Rails has rapidly become one of the most powerful and popular frameworks for building dynamic web applications. Rails users run the gamut from scrappy startups to huge companies: Posterous, UserVoice, 37signals, Shopify, Scribd, Twitter, Hulu, the Yellow Pages—the list of sites using Rails goes on and on. There are also many web development shops that specialize in Rails, such as ENTP, thoughtbot, Pivotal Labs, and Hashrocket, plus innumerable independent consultants, trainers, and contractors.

What makes Rails so great? First of all, Ruby on Rails is 100 percent open-source, available under the permissive MIT License, and as a result it also costs nothing to download and use. Rails also owes much of its success to its elegant and compact design; by exploiting the malleability of the underlying Ruby language, Rails effectively creates a domain-specific language for writing web applications. As a result, many common web programming tasks—such as generating HTML, making data models, and routing URLs—are easy with Rails, and the resulting application code is concise and readable.

Rails also adapts rapidly to new developments in web technology and framework design. For example, Rails was one of the first frameworks to fully digest and implement the REST architectural style for structuring web applications (which we'll be learning about throughout this tutorial). And when other frameworks develop successful new techniques, Rails creator David Heinemeier Hansson and the Rails core team don't hesitate to incorporate their ideas. Perhaps the most dramatic example is the merger of Rails and Merb, a rival Ruby web framework, so that Rails now benefits from Merb's modular design, stable API, and improved performance. (Anyone who has attended a talk by Merb developer and Rails core team member Yehuda Katz can't help but notice what an extremely good idea it was to bring the Merb team on board.)

Finally, Rails benefits from an unusually enthusiastic and diverse community. The results include hundreds of open-source contributors, well-attended conferences, a huge number of plugins and gems (self-contained solutions to specific problems such as pagination and image upload), a rich variety of informative blogs, and a cornucopia of discussion forums and IRC channels. The large number of Rails programmers also makes it easier to handle the inevitable application errors: the "Google the error message" algorithm nearly always produces a relevant blog post or discussion-forum thread.

1.1.1 Comments for Various Readers

Rails Tutorial contains integrated tutorials not only for Rails, but also for the underlying Ruby language, as well as for HTML, CSS, some JavaScript, and even a little SQL. This means that, no matter where you currently are in your knowledge of web development, by the time you finish this tutorial you will be ready for more advanced Rails resources, as well as for the more systematic treatments of the other subjects mentioned.

Rails derives much of its power from "magic"—that is, framework features (such as automatically inferring object attributes from database columns) that accomplish miracles but whose mechanisms can be rather mysterious. Ruby on Rails Tutorial is not designed to explain this magic—mainly because most Rails application developers never need to know what's behind the curtain. (After all, Ruby itself is mostly written in the C programming language, but you don't have to dig into the C source to use Ruby.) If you're a confirmed pull-back-the-curtain kind of person, I recommend The Rails 3 Way by Obie Fernandez as a companion volume to Ruby on Rails Tutorial.

Although this book has no formal prerequisites, you should of course have at least some computer experience. If you've never even used a text editor before, it will be tough going, but with enough determination you can probably soldier through. If, on the other hand, your .emacs file is so complex it could make a grown man cry, there is still plenty of material to keep you challenged. Rails Tutorial is designed to teach Rails development no matter what your background is, but your path and reading experience will depend on your particular circumstances.

All readers: One common question when learning Rails is whether to learn Ruby first. The answer depends on your personal learning style. If you prefer to learn everything systematically from the ground up, then learning Ruby first might work well for you, and there are several book recommendations in this section to get you started. On the other hand, many beginning Rails developers are excited about making web applications, and would rather not slog through a 500-page book on pure Ruby before ever writing a single web page. Moreover, the subset of Ruby needed by Rails developers is different from what you'll find in a pure-Ruby introduction, whereas Rails Tutorial focuses on exactly that subset. If your primary interest is making web applications, I recommend starting with Rails Tutorial and then reading a book on pure Ruby next. It's not an all-or-nothing proposition, though: if you start reading Rails Tutorial and feel your (lack of) Ruby knowledge holding you back, feel free to switch to a Ruby book and come back when you feel ready. You might also consider getting a taste of Ruby by following a short online tutorial, such as can be found at http://www.ruby-lang.org/ or http://rubylearning.com/.

Another common question is whether to use tests from the start. As noted in the introduction, Rails Tutorial uses test-driven development (also called test-first development), which in my view is the best way to develop Rails applications, but it does introduce a substantial amount of overhead and complexity. If you find yourself getting bogged down by the tests, feel free to skip them on first reading.4 Indeed, some readers may find the inclusion of so many moving parts—such as tests, version control, and deployment—a bit overwhelming at first, and if you find yourself expending excessive energy on any of these steps, don't hesitate to skip them. Although I have included only material I consider essential to developing professional-grade Rails applications, only the core application code is strictly necessary the first time through.

Inexperienced programmers (non-designers):Rails Tutorial doesn't assume any background other than general computer knowledge, so if you have limited programming experience this book is a good place to start. Please bear in mind that it is only the first step on a long journey; web development has many moving parts, including HTML/CSS, JavaScript, databases (including SQL), version control, and deployment. This book contains short introductions to these subjects, but there is much more to learn.

Inexperienced programmers (designers): Your design skills give you a big leg up, since you probably already know HTML and CSS. After finishing this book you will be in an excellent position to work with existing Rails projects and possibly start some of your own. You may find the programming material challenging, but the Ruby language is unusually friendly to beginners, especially those with an artistic bent.

After finishing Ruby on Rails Tutorial, I recommend that newer programmers read Beginning Ruby by Peter Cooper, which shares the same basic instructional philosophy as Rails Tutorial. I also recommend The Ruby Way by Hal Fulton. Finally, to gain a deeper understanding of Rails, I recommend The Rails 3 Way by Obie Fernandez.

Web applications, even relatively simple ones, are by their nature fairly complex. If you are completely new to web programming and find Rails Tutorial overwhelming, it could be that you're not quite ready to make web applications yet. In that case, I'd suggest learning the basics of HTML and CSS and then giving Rails Tutorial another go. (Unfortunately, I don't have a personal recommendation here, but Head First HTML looks promising, and one reader recommends CSS: The Missing Manual by David Sawyer McFarland.) You might also consider reading the first few chapters of Beginning Ruby, which starts with sample applications much smaller than a full-blown web app.

Experienced programmers new to web development: Your previous experience means you probably already understand ideas like classes, methods, data structures, etc., which is a big advantage. Be warned that if your background is in C/C++ or Java, you may find Ruby a bit of an odd duck, and it might take time to get used to it; just stick with it and eventually you'll be fine. (Ruby even lets you put semicolons at the ends of lines if you miss them too much.) Rails Tutorial covers all the web-specific ideas you'll need, so don't worry if you don't currently know a PUT from a POST.

Experienced web developers new to Rails: You have a great head start, especially if you have used a dynamic language such as PHP or (even better) Python. The basics of what we cover will likely be familiar, but test-driven development may be new to you, as may be the structured REST style favored by Rails. Ruby has its own idiosyncrasies, so those will likely be new, too.

Experienced Ruby programmers: The set of Ruby programmers who don't know Rails is a small one nowadays, but if you are a member of this elite group you can fly through this book and then move on to The Rails 3 Way by Obie Fernandez.

Inexperienced Rails programmers: You've perhaps read some other tutorials and made a few small Rails apps yourself. Based on reader feedback, I'm confident that you can still get a lot out of this book. Among other things, the techniques here may be more up to date than the ones you picked up when you originally learned Rails.

Experienced Rails programmers: This book is unnecessary for you, but many experienced Rails developers have expressed surprise at how much they learned from this book, and you might enjoy seeing Rails from a different perspective.

After finishing Ruby on Rails Tutorial, I recommend that experienced (non-Ruby) programmers read The Well-Grounded Rubyist by David A. Black, which is an excellent in-depth discussion of Ruby from the ground up, or The Ruby Way by Hal Fulton, which is also fairly advanced but takes a more topical approach. Then move on to The Rails 3 Way to deepen your Rails expertise.

At the end of this process, no matter where you started, you will be ready for the more intermediate-to-advanced Rails resources. Here are some I particularly recommend:

Rails Guides: Good topical and up-to-date Rails references. Rails Tutorial refers frequently to the Rails Guides for more in-depth treatment of specific topics.

Rails blogs: Too many to list, but there are tons of good ones.

1.1.2 "Scaling" Rails

Before moving on with the rest of the introduction, I'd like to take a moment to address the one issue that dogged the Rails framework the most in its early days: the supposed inability of Rails to "scale"—i.e., to handle large amounts of traffic. Part of this issue relied on a misconception; you scale a site, not a framework, and Rails, as awesome as it is, is only a framework. So the real question should have been, "Can a site built with Rails scale?" In any case, the question has now been definitively answered in the affirmative: some of the most heavily trafficked sites in the world use Rails. Actually doing the scaling is beyond the scope of just Rails, but rest assured that if your application ever needs to handle the load of Hulu or the Yellow Pages, Rails won't stop you from taking over the world.

1.1.3 Conventions in This Book

The conventions in this book are mostly self-explanatory; in this section, I'll mention some that may not be. First, both the HTML and PDF editions of this book are full of links, both to internal sections (such as Section 1.2) and to external sites (such as the main Ruby on Rails download page).5

Second, your humble author is a Linux/OS X kind of guy, and hasn't used Windows as his primary OS for more than a decade; as a result, Rails Tutorial has an unmistakable Unix flavor.6 For example, in this book all command line examples use a Unix-style command line prompt (a dollar sign):

$ echo "hello, world"hello, world

Rails comes with lots of commands that can be run at the command line. For example, in Section 1.2.5 we'll run a local development web server as follows:

$ rails server

Rails Tutorial will also use Unix-style forward slashes as directory separators; my Rails Tutorial sample app, for instance, lives in

/Users/mhartl/rails_projects/first_app

The root directory for any given app is known as the Rails root, and henceforth all directories will be relative to this directory. For example, the config directory of my sample application is in

/Users/mhartl/rails_projects/first_app/config

This means that when referring to the file

/Users/mhartl/rails_projects/first_app/config/routes.rb

I'll omit the Rails root and write config/routes.rb for brevity.

Finally, Rails Tutorial often shows output from various programs (shell commands, version control status, Ruby programs, etc.). Because of the innumerable small differences between different computer systems, the output you see may not always agree exactly with what is shown in the text, but this is not cause for concern. In addition, some commands may produce errors depending on your system; rather than attempt the Sisyphean task of documenting all such errors in this tutorial, I will delegate to the "Google the error message" algorithm, which among other things is good practice for real-life software development.